With current microphone technology, frequency response of the microphone is often problematic. The signal to noise ratio (SNR) of the microphone is defined by the noise integrated in the area under the frequency response curve, and therefore it is desirable that the resonant peak frequency is not in the range of audible frequencies of interest. MEMS microphones typically have a resonant peak frequency around 20 kilohertz (kHz) in an integrated package. However, it is desirable to push the resonant peak frequency out to a higher value.
Another problem associated with conventional MEMS microphones is that the sound pressure level at which final mechanical clipping occurs is not as high as would be desired. As such, the highest sound pressure level (SPL) that can be received by a diaphragm of a microphone and properly converted into an electrical signal without distortion is less than desired. Specifically, in conventional MEMS microphones, distortion will be experienced at a SPL of 135 decibels dB SPL, which means that 135 dB SPL is the final mechanical clipping point of the microphone. A MEMS microphone with a higher final mechanical clipping point (in terms of SPL value) would be desirable.
Yet another problem associated with conventional MEMS microphones is percent distortion for a defined SPL. For example, approximately 1% of distortion is obtained for sound pressure that reaches the 120 dB SPL mark. It is desirable to have a higher sound pressure level before such distortion is experienced. Increasing the final mechanical clipping point would also reduce the distortion levels at SPL levels that are below the final clipping point.